Abstract: A system is disclosed for verifying the operativeness of a crowbar circuit which normally protects an electrical device in a series circuit with a power supply. The crowbar circuit includes means for sensing fault current in the series circuit and a crowbar switch responds to the sensing means for protecting the electrical device by directing the fault current away from the electrical device. The system includes verification testing means including a fuse and actuatable pneumatic switch connected together in series for, when said pneumatic switch is actuated, providing a short circuit across the crowbar switch to verify the operativeness of the crowbar circuit which, if not operative, causes the fault current to flow through and blow out the fuse.

Abstract: A substantially constant impedance is developed across the input terminals of a linear amplifier used in a very high frequency (VHF) low band television transmitter. The input circuit consists of lumped components arranged in a capacitively coupled double tuned configuration. A relatively long coaxial transmission line system is used to connect the input circuit to the terminals of the tube. The coaxial line system and input circuit tunes across the entire VHF low band of 54 to 88 MHz. An input voltage standing wave ratio (VSWR) equal to or less than 1.2:1 is achieved over each six MHz channel.

Abstract: An output coaxial cavity for high power electron tubes is described in which the output coupler is directly connected to an intermediate coaxial conductor of the coaxial cavity at a distance from the tube that is greater than one-quarter wavelength and less than one-half wavelength over the tuning range of the cavity. The intermediate coaxial conductor is spaced between and concentric with an inner conductor and an outer conductor of the coaxial cavity. A first shorting stub is positioned between the inner conductor and the intermediate conductor and a second shorting stub is coupled between the intermediate conductor and the outer conductor. The positions of the shorting stubs are arranged to resonate the cavity at the desired tuning frequency.